1. Field of the invention
The present invention relates to an automotive air-conditioning system and, more specifically, to an automotive air-conditioning system capable of obviating the adverse influence of insolation on air-conditioning control during a period from the start of the blower to a time when the blowing rate of the blower reaches the normal level so that agreeable air-conditioning is achieved.
2. Description of the Prior Art
A conventional automotive air-conditioning system is illustrated in FIG. 3. As shown in FIG. 3, a duct 1 is provided with a selector door 2 for selectively establishing the fresh air intake mode or the room air recirculating mode, a blower 3, an evaporator 4, an air mixing door 5, a heater core 6, mode changing doors 7, a window defrosting opening 8, a center opening 9 and a foot opening 10. The heat exchanger 4, a compressor 11, a condenser 12, a receiver tank 13 and an expansion valve 14 constitute a cooling system. The compressor 11 is connected through a magnetic clutch 16 to the engine 15. An AD converter 17 receives analog signals representing room temperature Tr detected by a room temperature sensor 18, an opening .theta. of the air mixing door detected by a potentiometer 19, intensity of insolation Ts detected by an insolation sensor 20, fresh air temperature Ta detected by a fresh air temperature sensor 21, evaporator temperature Tm detected by a temperature sensor 22 and set temperature Td provided by a temperature setting unit 23, and gives the corresponding digital signals to a control unit 24.
The control unit 24 is a computerized control unit comprising a selector door control means 27 for controlling the selector door 2 through a changeover circuit 25 and an actuator 26, a compressor control means 29 for controlling the magnetic cluth 16 through a driving circuit 28, a blower control means 31 for controlling the blower 3 through a driving circuit 30, an air mixing door control means 34 and an actuator 33, a mode changing door control means 37 for controlling the mode changing doors 7 through a changeover circuit 35 and an actuator 36, and a central data processing means 38 which processes the data corresponding to room temperature Tr, intensity of insolation Ts, fresh air temperature Ta, evaporator temperature Tm and set temperature Td, and which gives blows signals T to the control means 27, 29, 31, 34 and 37. Indicated at 39 is a manual switch.
The blower 3 is controlled by the blower control means 31 on the basis of the combined signals T so that the blower blowes air at a blowing rate corresponding to the combined signals T. The air mixing door 5 is controlled by the air mixing door control means 34 so that the opening .theta. of the air mixing door 5 corresponds to the combined signals T. The mode changing door 7, the changeover circuit 35, the actuator 36 and the mode changing door control means 37 constitute a mode changing means 40. The mode changing means 40 controls the mode changing doors 7 on the basis of a mode changing signal TOF represented by Expression (1) to establish a defrosting mode where conditioned air is blown through the window defrosting opening 8, a face mode where conditioned air is blow through the center opening 9, a foot mode where conditioned air is blow through the foot opening 10 or a bilevel mode where conditioned air is blown through both the center opening 9 and the foot opening 10. EQU TOF=Tm+K.theta.+.beta. (1)
where K and .beta. are constants.
This conventional automotive air-conditioning system functions in the following manner.
When an air-conditioner switch and a fan switch are operated, the blower 3 is started and a predetermined air-conditioning control program is executed on the basis of the combined signals T and the mode changing signal TOF. During the initial stage of air-conditioning immediately after the operation of the air-conditioning switch and the fan switch, namely, immediately after the start of the blower 3, the blowing rate of the blower 3 is increased gradually for agreeable air-conditioning in the heating mode. Therefore, the actual blowing rate of the blower 3 does not rise immediately to a blowing rate corresponding to the combined signal T and reaches the blowing rate corresponding to the combined signals T with a time lag. During this initial stage where the actual blowing rate does not coincide with the blowing rate corresponding to the combined signals T, the following problems arise.
Suppose that insolation Ts is high when fresh air temperature Ta is low and heating is required accordingly. Then, the combined signals T is affected greatly by insolation Ts, and thereby the air mixing door 5 is turned to a position corresponding to the full cooling mode. The variation of the opening of the air mixing door 5 causes the mode changing door control means 37 to control the mode changing doors 7 according to TOF determined by Exp. (1) to establish the face mode.
Consequently, warm air is not blown through the foot opening 10, while the fresh air temperature Ta is low and hence heating is necessary, which does not meet conditions for agreeable air-conditioning.
A device relating to an automotive air-conditioning system is disclosed in U.S. Pat. No. 4,262,738 and Japanese Utility Model Publication No. 54-37104, however, this device is unable to solve the above-mentioned problem.